This invention relates to agricultural dispensing mechanisms for dispensing agricultural particulate material, and to agricultural implements incorporating such dispensing mechanisms for delivering to the ground agricultural particulate materials such as seeds, fertilizers, herbicides, insecticides, nematicides, fungicides, slug pellets and other pesticides. Examples of such implements are seed drills, seed and fertilizer drills, fertilizer dispensers for precision rowcrop planters such as planters for maize, soya beans, potatoes etc., and rotary cultivators adapted to plant row crops.
More particularly, this invention relates to agricultural dispensing mechanisms comprising a resilient dispensing roller to dispense the agricultural particulate material.
Previous proposals relating to dispensing mechanisms having a resilient dispensing roller include proposals to use such a roller in portable hand-operated devices for spreading material such as lawn fertilizer over the entire surface of an area to be treated. The material specified for the roller in these proposals has been foam or sponge rubber, i.e. rubber expanded by gas bubbles. We have found that this material has certain operational disadvantages which are explained below, but since the standard of accuracy, consistency, and reproducibility of performance expected from devices such as portable lawn fertilizer spreaders is low, such disadvantages have not been noticeable in those particular implements.
Where dispensing rollers of expanded rubber have been tested in agricultural row crop implements such as seed drills however, the high standards of accuracy, consistency, and reproducibility of performance expected of such implements have highlighted the operational disadvantages referred to above. These disadvantages include firstly variations in the flexibility and hardness of the expanded rubber inherently arising from the method of expanding the rubber in manufacture, secondly variations in such physical characteristics of the roller as flexibility and hardness with changes in temperature during use (such temperature changes affecting the gas pockets in the rubber), thirdly variations of the physical characteristics of the roller and shrinkage of the roller with time i.e. ageing of the expanded rubber, and fourthly the susceptibility of the expanded rubber to damage by moisture (especially upon freezing) and by abrasive materials such as certain fertilizers and certain sharp seeds.
These variations in the physical characteristics of the dispensing rollers change their performance when dispensing particulate material, which is undesirable.
However, resilient roller dispensing mechanisms of the kind disclosed in British Pat. No. 1,525,566 have such significant inherent technical advantages over alternative mechanisms having rigid rollers of the peg or fluted type that the provision of an improved resilient roller in which some or all of the above mentioned disadvantages are overcome would be a valuable contribution to the art.
Improvement of the quality of the expanded rubber of the rollers itself is expensive and difficult to achieve from a production point of view, and would not remove the disadvantages inherent in the use of foam rubber anyway. Use of an unfoamed solid rubber, even of very soft rubber, nevertheless seriously restricts the versatility of the mechanism making it unsatisfactory for dispensing particles larger than small seeds. This is because the solid rubber has to be displaced by each particle dispensed and in the case of large seeds such displacement seriously distorts the roller making it either jam on adjacent structures or making it locally non-cylindrical thereby interfering with the proper dispensing of adjacent seeds, or else the forces generated by displacement of the rubber damage the seed. It is a very important feature of such a seed dispensing mechanism that it can properly handle a wide range of seed sizes.
Thus it is a broad objective of the present invention to provide an agricultural dispensing mechanism having a resilient dispensing roller for dispensing particulate material such as seed or fertilizer, the roller having better performance or life characteristics than currently available rollers of expanded rubber. More specific objectives include the provision of a roller for such a dispensing mechanism which can be more easily made to a consistent standard of performance, which is more durable in use, and which can be readily formed with an appropriate surface finish.